If BC is a diameter of a circle with centre O and OD is perpendicular to the chord AB of a circle, then CA = ____ OD.
If BC is a diameter of a circle with centre O and OD is perpendicular to the chord AB of a circle, show that CA=2 OD.
In the adjoining figure, OD is perpendicular to the chord AB of a circle with centre O. If BC is a diameter, show that AC||DO and AC=2×OD.